COLUMN ONE : Gangs Find Fresh Turf in Salvador : Whether by choice or by force, many L.A. youths have returned to their homeland bringing with them a violent subculture. It's taken root among disaffected teen-agers primed by years of war.

SANTA TECLA, El Salvador — The teen-agers crowding at the edge of the central plaza flash hand signs, share a marijuana joint and swap stories of the previous night's exploits. Dressed in baggy pants, their arms and chests covered with tattoos, their hair slicked back, they speak a street Spanish mixed with street English and call each other by gang nicknames.

"Whassup, home?"

Meet the Hollywood Locos gang--El Salvador branch.

The latest product of the longstanding social and economic ties between El Salvador and the United States, especially Southern California, is something neither side is particularly eager to claim: a rapidly expanding and increasingly violent gang subculture.

Gangs formed by Salvadorans in Los Angeles have long been considered among the most ruthless and deadly. But with El Salvador's civil war finally winding down, members of those gangs have been returning here--some by choice, many by force, as immigration authorities step up deportation of convicted felons and other lawbreakers.

They bring with them their murderous ways and brutal rituals. They recruit among El Salvador's abundant disaffected youth, form new gangs or co-opt the existing school-based gangs. Law enforcement authorities say the gangs are partly responsible for a huge surge in crime that is terrorizing Salvadorans just as they struggle to recover from war.

"We are finding, every day, more and more influence from the Los Angeles gangs--the way they dress, the way they celebrate, their ceremonies. . . ," said national deputy police chief Rodrigo Avila. "The internationalization of these gangs is a scary thing."

The graffiti common in Los Angeles neighborhoods have sprouted up all over San Salvador, in this suburb of the capital and even in the smallest rural towns. Some of the graffiti welcome "homeboys"--in English.

Versions of several Los Angeles gangs now exist in El Salvador, including the notorious Mara Salvatrucha and its principal enemy, 18th Street.

The phenomenon is not limited to this country. Police in Belize, for example, report the arrival of alleged members of the Crips and Bloods gangs. But nowhere has the importation of gangs flourished as it has here.

Postwar Salvadoran society is enormously fertile ground for gangs: This is a cruelly violent country where guns, grenades and other weapons abound. Unemployment is high and opportunity low, especially for youths. The war and the migration of more than 1 million Salvadorans in the last decade have left families broken, parents separated from children and children deprived of authority figures or role models.

And in a curious case of reverse culture shock, many of the Salvadoran gangsters who are returning to El Salvador spent most of their lives in the United States. They know Western or Normandie better than San Salvador's Plaza Libertad. They come here barely able to speak Spanish and with few ties to the local community, making the gang network all the more crucial to what they see as their survival.

Ominously, they also bring with them the same deadly rivalries that they had in the States.

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Jose Amaya, a shaven-headed member of Mara Salvatrucha, says he was deported from Los Angeles in March after finishing a two-year prison sentence for drug dealing. He had lived in California for 19 of his 20 years and was arrested three times before being deported.

"I don't like it here," he said. "All my life is in L.A. My family is there. My money is better there. I got enemies here. Like I been deported, they been deported. He's my enemy in L.A., he's my enemy here too. So I kick with my homeboys."

Amaya was holding court around midnight recently outside the main pavilion of San Salvador's International Fairgrounds. Weekend concerts and dances at this site have become the gangs' favorite legal entertainment; it's a place to gather, get drunk and plot ways to kill adversaries. Hundreds attend, to the chagrin of residents and police. Some gangs even charter buses for followers from rural hometowns.

On this Saturday night, agents from the paramilitary National Police formed a cordon outside the pavilion and rounded up about 25 boys who looked like gang wanna-bes. They wore baggy pants and long T-shirts, but most were younger than 16 and not armed. Older boys hid the weapons.

Police-- la chota in gang slang--loaded the detainees into a pickup truck. As it pulled away, the boys flashed their hands in the shape of an "M" for mara , the Spanish slang for gang , and shouted, "M.S., rifa!" "Mara Salvatrucha rules!"

Because they are minors, the boys eventually will be released.

Gangs have existed in El Salvador since the late 1950s, but until recently they were more likely to be associated with schools and would fight each other over things like basketball games, perhaps over territory, but not over business interests or crime franchises.